In an attempt to answer the question on StackExchange Arduino, What type of connector does the GROVE system use?, and after looking up the Grove system, I contacted the technical support team at Seeed. I promptly had a reply, and below is the information that I received.
This is the datasheet (PDF) on the connector that I was sent: 110990030-model
Here is a screenshot of the datasheet,
I also received this, somewhat cryptic, information:
Grove – Light Sensor change to V1.2, which had another light sensor.
Just some performance optimization.
From ebay, Grove – SMD Universal 4 pin connector (10 Stück), here is another diagram of a connector, although the diagram clearly shows only a three pin connector, and not the four pin connector used in the Grove system::